Fluorescent compounds have been excellent tools for the sensitive and specific detection of a variety of analytes (De Silva et al., “Signaling Recognition Events with Fluorescent Sensors and Switches,” Chem Rev 97:1515-1566 (1997)). While the rational approach in designing the fluorescent sensors was successful toward diverse small molecule analytes (Gabe et al., “Highly Sensitive Fluorescence Probes for Nitric Oxide Based on Boron Dipyrromethene Chromophore-Rational Design of Potentially Useful Bioimaging Fluorescence Probe,” J Am Chem Soc 126:3357-3367 (2004); Chang et al., “A Selective, Cell-Permeable Optical Probe for Hydrogen Peroxide in Living Cells,” J Am Chem Soc 126:15392-15393 (2004); Burdette et al., “Fluorescent Sensors for Zn(2+) Based on a Fluorescein Platform: Synthesis, Properties and Intracellular Distribution,” J Am Chem Soc 123:7831-7841 (2001); Schneider et al., “Coupling Rational Design with Libraries Leads to the Production of an ATP Selective Chemosensor,” J Am Chem Soc 122:542-543 (2000)), the combinatorial approach to fluorescent dyes has shown powerful advantages owing to a wide range of spectral and structural diversity, developing specific binders for macromolecule structures with a concomitant change of fluorescence properties (Rosania et al., “Combinatorial Approach to Organelle-Targeted Fluorescent Library Based on the Styryl Scaffold,” J Am Chem Soc 125:1130-1131 (2003); Lee et al., “Development of Novel Cell-Permeable DNA Sensitive Dyes Using Combinatorial Synthesis and Cell-Based Screening,” Chem Commun (Camb) 15:1852-1853 (2003); Li et al., “Solid-Phase Synthesis of Styryl Dyes and Their Application as Amyloid Sensors,” Angew Chem Int Ed Engl 43(46):6331-6335 (2004); Li et al., “RNA-Selective, Live Cell Imaging Probes for Studying Nuclear Structure and Function,” Chem Biol 13(6):615-623 (2006)).
The present invention is directed to an improved class of fluorescent compounds.